Trade Comissions

#include <iostream>
#include <cmath>
using namespace std;

int main(){

    string city;
    double sales, comission;
    cin >> city >> sales;

    if (city == "Sofia"){
        if (sales >= 0 && sales <= 500){
            comission = 0.05;
        } else if ( sales > 500 && sales <= 1000){
            comission = 0.07;
        } else if ( sales > 1000 && sales <= 10000){
            comission = 0.08;
        } else if ( sales > 10000){
            comission = 0.12;
        }
    } else if (city == "Varna"){
        if (sales >= 0 && sales <= 500){
            comission = 0.045;
        } else if ( sales > 500 && sales <= 1000){
            comission =  0.075;
        } else if ( sales > 1000 && sales <= 10000){
            comission =  0.10;
        } else if ( sales > 10000){
            comission = 0.13;
        }
    } else if (city == "Plovdiv"){
        if (sales >= 0 && sales <= 500){
            comission =  0.055;
        } else if ( sales > 500 && sales <= 1000){
            comission =  0.08;
        } else if ( sales > 1000 && sales <= 10000){
            comission = 0.12;
        } else if ( sales > 10000){
            comission = 0.145;
        }
    } else {
        comission = -50;
    }

    if (comission >= 0){
        cout.setf(ios::fixed);
        cout.precision(2);
        cout << comission * sales << endl;
    } else {
        cout << "error" << endl;
    }

return 0;

}